How Stainless-Steel Stations Provide Safe Solvent Processing

Solvents used in semiconductor manufacturing can remove and organic contaminants from silicon wafers in preparation for further processing steps.

Acetone, isopropyl alcohol (IPA) and ethylene diproxitol (EDP) are solvents commonly used to clean wafers, remove photoresist and in pattern transfers for the creation of microscopic structures on the wafer.

But since these solvents are also inflammable, they require special safety measures to reduce the risk of fire and explosion, and they have to be disposed of safely. Stainless steel wet benches incorporating stainless steel processing tanks are designed with features that provide safe processing of solvents.

Safe operation of stainless-steel solvent stations has to include the following safety measures:

·         Fire suppression – Measures can include electrical design limiting the potential energy of sparks so they can’t ignite solvents and designing equipment to Class 1, Division 2 specifications

·         Fire fighting – It has to be able to extinguish fires. For inflammable liquids such as solvents, gas-type fire systems such as those using carbon dioxide are needed.

·         Protection against exposure – Many solvents are harmful when workers are exposed to them over extended periods, either through direct contact or through breathing the fumes. A complete enclosure of the solvent processing tanks along with effective exhausts limits the amount of solvent to which workers can be exposed.

·         Protection against leaks – A complete enclosure of the solvent processing tanks should also have a leak detection feature.

·         Safe disposal – Disposal of used solvents has to be carried out safely and according to environmental regulations. Disposal can be on site, if the facility has the corresponding capability, or the waste can be stored in a carboy for pick-up by a specialized disposal company.

Modutek’s stainless steel stations are made of 304 stainless steel and are available in fully automatic, semi-automatic, or manual versions. Dry to dry and fume hood designs are possible, and the stations feature casters and leg levelers.

Modutek’s semi-automated and fully automated wet benches have a built-in SolidWorks simulation software that calculates the process flow characteristics, and all design, assembly, and testing is carried out in-house. As a leading wet bench manufacturer, Modutek works closely with customers to design and customize equipment to meet each client’s requirements.

For more details read the complete article, “How Stainless-Steel Stations Provide Safe Solvent Processing”. If you have questions after reading the article or would like to set up a free consultation to discuss your particular needs, contact Modutek via email Sales@Modutek.com or by calling 866-803-1533.

How Teflon Tanks Improve the KOH Etching Process

Etching silicon wafers with potassium hydroxide (KOH) is a popular process for semiconductor manufacturing. It is relatively safe compared to other etching methods and features good control of the etch rate. When carried out in Teflon tanks, contamination is reduced and the etch rate can be controlled.

Determining the required etch rate is the key factor for a successful etching. An etch rate that’s too fast may mean that the KOH may etch too far into the silicon. But an etch rate that’s too slow may result in a shallow etch. Improving the KOH etching process means applying several control methods to the etch rate to ensure the resulting shapes are exactly correct.

The process factors that may affect the KOH etch rate:

·         Process temperature – The higher the temperature of the KOH solution, the faster that the KOH will etch the silicon.

·         Solution concentration – A higher concentration increases the etch rate.

·         Doping – It means adding impurities to the silicon crystal. When boron is placed into the silicon crystal lattice at a specific location, etching stops in that direction. Boron doping can influence the shapes to be etched this way.

·         Crystal lattice orientation – The silicon crystal atoms are arranged in a cubic lattice that has a greater atom density in some directions than in others. Etching is slower in directions with a higher atom density.

All four factors mentioned above need to be taken into account when designing the mask to obtain the microscopic silicon structures. The silicon wafer needs to be oriented correctly to give the different etch rates along with different lattice directions. Doping has to be in place where etching needs to stop, and the correct concentration of KOH solution has to used. These initial conditions need to be established before starting the process.

A target temperature can also be set, but the temperature will be varied to adjust the etch rate during processing. The ability to alter the etch rate by changing the temperature provides excellent control of the KOH etching process.

Modutek’s Teflon tanks provide precise control of the KOH etching process and are available in a circulating or a static design. The heat source can either be inline or immersed in the overflow weir. An all-Teflon liquid path design reduces the possibility of contamination. The use of heated tanks improves the KOH etching process with short heat up times and precise temperature control.

For more details read the complete article, “How Teflon Tanks Improve the KOH Etching Process”. Contact Modutek for free consultation to discuss your needs at 866-803-1533 or email Sales@Modutek.com.

How On-Site Acid Neutralization Provide Safe Chemical Disposal

 

Choosing the right acid neutralization system is crucial. With overall standards getting tighter, it is important to have a system that can automatically add the required neutralizing chemicals to acid waste left over once the semiconductor process step is done.

Such a system should use the least amount of chemicals while ensuring adequate neutralization of waste to comply with the environmental standards. It has to have enough capacity to handle the waste chemical flow. It must also operate reliably, protecting against spills and documenting chemical use and discharge.

Automated acid neutralization systems can operate in either two ways:

·         Continuous flow – this is ideal for large-scale operations. Because the nature of the waste chemicals is known and remains consistent over time, the neutralization process can add fixed amounts of low-pH chemicals to continuously neutralize the waste flow.  Neutralization can be fine-tuned because the overall process doesn’t change.

·         Batch – this is better suited for the production of small quantities of semiconductor products. Typical applications are prototype production, production of small quantities for testing or the manufacture of special components. In this system, the waste chemicals have to be neutralized in small batches. Each process is different. This type of system has to measure the pH of the waste chemicals and determine what low-pH additions are appropriate. The neutralization is different for each batch as is each outflow.

Complete automation of a continuous flow comparatively easy because the process parameters are known and don’t change. The automation only has to add the required amount of neutralizing chemical on a continuous basis and record the resulting pH.

However, doing a complete automation of batch neutralization systems, however, can be challenging. The key variables, the process, and the chemicals involved can vary depending on the batch. First, it has to measure the batch pH and add an amount of low-pH neutralizer. Depending on the chemicals involved, the automated system may have to add different neutralizing chemicals in several stages to achieve the required output. Compared to a fully automated continuous flow system, a fully automated batch neutralization system is complicated to program and difficult to set up. Operator involvement to select the type of neutralization required can simplify the process of the automated system, making it more effective.

Automated acid neutralization systems can help reduce chemical use, reduce spills, and ensure regulatory compliance. The system automatically adds the required chemicals to the waste solution, tracks chemical use, measures outflow pH, and records the results. As a result, workplace safety is increased, and human error is reduced. The records of chemical use and outflow pH can show that the environmental standards are met.

Modutek offers a full line of chemical handling equipment, along with acid neutralization systems. Read their complete article, “How On-Site Acid Neutralization Systems Provide Safe Chemical Disposal”. If you have questions, or would like to set up a free consultation, send an email to Sales@modutek.com or call 866-803-1533.